Petrogenesis and source characteristics of Permian picrites and basalts in Muli area, Sichuan Province

Abstract：Nuremous papers have been published for Emeishan Permian basalts; nevertheless, some key scientific problem, such as magma source components and P-T conditions, remain problems of hot debate. This paper reported petrologic, geochemical and Sr-Nd isotopic data of the Permian picrites and related basalts in Muli area of eastern Sichuan, and discussed magma source characteristics and P-T conditions of these volcanic rocks. The authors have detected that main rock types are picrites and high-Ti and Low-Ti basalts. Picritic magmas were probably derived from the high temperature area at the center of the plume head (the axial zone of mantle plume) and melted within the garnet stable field. However, high-Ti and low-Ti basaltic magmas were probably derived from the mantle plume tail area. High-Ti basalts were mainly melted within the garnet stable field, but the low-Ti basalts were probably melted around the garnet-spinel transition. Both picritic and basaltic magmas were mixed with a subcontinental lithospheric mantle (SCLM) in various degrees during their upward migration, and the low-Ti basaltic magmas might have been contaminated by crust materials.